Futon mattress



FIG. 1 is a perspective view of a futon mattress, showing our new design; the broken lines are for environmental purposes only and form no part of the claimed design.

FIG. 2 is a perspective view of the futon mattress without the frame, showing the end detail;

FIG. 3 is a perspective view of the mattress in a flat position;

FIG. 4 is a front elevational view thereof the rear being identical thereto;

FIG. 5 is a side elevational view thereof the opposite side being a mirror image thereof;

FIG. 6 is a top plan thereof; and,

FIG. 7 is a bottom plan view thereof. 

The ornamental design for a futon mattress, as shown and described. 